In film-based image sensors, a silicon-based readout integrated circuit (ROIC) is overlaid with a photosensitive film, such as a film containing a dispersion of quantum dots (referred to herein as a “quantum film”). The ROIC comprises a switching array, which can be similar to those used in complementary metal-oxide semiconductor (CMOS) image sensors that are known in the art. The switching array includes an array of pixel electrodes, which contact the film in order to read out the photocharge that accumulates in each pixel of the film due to incident light. A common electrode, which is at least partially transparent, is formed over the photosensitive film.
A metallization layer contacts the common electrode in order to apply a bias potential across the film. The metallization layer, which is typically opaque, covers a part of the common electrode and the underlying film, and may optionally cover one or more of the pixels in order to provide an optically-black level for purposes of black-level correction. The edge of the film and overlying common electrode are typically etched away from the ROIC before deposition of the metallization layer in order to enable the metallization layer to contact a built-in pad (BIP), through which the bias potential can then be applied to the metallization layer.